1. Field of the Invention
The invention relates to a device for generating ozone from oxygen or an oxygen-containing gas by silent electric discharges in a discharge gap through which the gas flows and which is essentially formed by a tubular outer electrode and an inner electrode concentrically surrounded by the outer electrode, a dielectric which separates the electrodes from one another being arranged in the discharge gap, and metallic spring elements being provided for spacing the dielectric from the outer electrode.
In this connection, the invention refers to a prior art as can be found, for example, in French Patent Specification 2,424,874.
2. Discussion of Background
Ozone is a very strong oxidant for organic substances and for inorganic compounds which contain elements having several oxidation numbers. Apart from a large variety of applications in chemistry, it has been used for decades in water conditioning. However, the high investment and operating costs for ozone generation restrict the possible applications.
Although, theoretically, there are many possibilities of generating ozone, it has hitherto only been ozone generation by silent electric discharge which, in practice, has gained any significance.
In contrast to plate-type ozone generators, problems of ensuring accurate spacing of the electrodes arise in the case of tube-type ozone generators. This is caused mainly by dimensional deviations of the tube diameters and by bending.
In German Offenlegungsschrift 3,422,989 a possibility of ensuring accurate concentric coordination between inner electrode, dielectric and outer electrode is described. The spacers described and shown there consist of a plastic band bonded in spiral form to the inner electrode. Apart from the spacing, the spiral application results in an increase in the gas velocity and improves cooling.
As a rule, these bands consist of polytetrafluoroethylene (Teflon). Plastic bands, particularly those of polytetrafluoroethylene, however, tend to flow during the operation of the ozone generator so that they cannot fulfill their spacing function to the desired extent. In addition, their stability in the discharge is inadequate.
From French Patent Specification 2,424,874, an ozone generator is known in which the dielectric tube is spaced apart from the outer metal tube by means of spring tongues which are joined integrally to a carrier slotted in the longitudinal direction of the tube. Carrier and spring tongues consist of an elastic ozone-resistant metal. With the currently used gap widths of 1 millimeter and less, these spacing elements narrow the discharge gap and thus impede the flow of the operating gas. Because, on the one hand, a minimum spring effect of the tongues and, on the other hand, a fixing of the carrier on the dielectric tube or in the outer metal tube must be ensured, the thickness of the carrier material and thus of the spring tongues cannot be made arbitrarily small. Furthermore, the spring characteristics of the spring tongues are highly dependent on their geometry. The smallest deviations from the predetermined angle at which the spring tongues are bent out of the carrier influence the spacing. Moreover, the installation of the dielectric tubes provided with the spacing elements or, respectively, the insertion of the dielectric tubes into the metal tubes equipped with said elements requires complicated assembly aids.